diff --git a/sbin/dmesg/dmesg.c b/sbin/dmesg/dmesg.c
index f0fcb8125877..9fee41664b30 100644
--- a/sbin/dmesg/dmesg.c
+++ b/sbin/dmesg/dmesg.c
@@ -111,8 +111,10 @@ main(int argc, char *argv[])
 
 	if (memf == NULL) {
 		/*
-		 * Running kernel.  Use sysctl.  This gives an unwrapped
-		 * buffer as a side effect.
+		 * Running kernel.  Use sysctl.  This gives an unwrapped buffer
+		 * as a side effect.  Remove nulterm (if present) so the value
+		 * returned by sysctl is formatted as the rest of the code
+		 * expects (the same as the value read from a core file below).
 		 */
 		if (sysctlbyname("kern.msgbuf", NULL, &buflen, NULL, 0) == -1)
 			err(1, "sysctl kern.msgbuf");
@@ -120,6 +122,8 @@ main(int argc, char *argv[])
 			errx(1, "malloc failed");
 		if (sysctlbyname("kern.msgbuf", bp, &buflen, NULL, 0) == -1)
 			err(1, "sysctl kern.msgbuf");
+		if (buflen > 0 && bp[buflen - 1] == '\0')
+			buflen--;
 		if (clear)
 			if (sysctlbyname("kern.msgbuf_clear", NULL, NULL, &clear, sizeof(int)))
 				err(1, "sysctl kern.msgbuf_clear");